code: def testFileDoesntExist(self):
      file_path = os.path.join(self._base_dir, "temp_file")
      self.assertFalse(gfile.exists(file_path))
      with self.assertRaises(errors.NotFoundError):
          _ = gfile._read_file_to_string(file_path)
  
imports: import os.path
  from tensorboard import test
  from tensorboard.compat.tensorflow_stub import compat, errors
  from tensorboard.compat.tensorflow_stub.io import gfile
label_desc: Use image node_id 3 for calling the FileIoTest obj's underlying member method code with example usage: obj.testFileDoesntExist() without return types